Step actuator

ABSTRACT

A step actuator includes a housing, a stator in the housing, a rotor including a magnet provided radially inward of the stator and a nut member inserted into the magnet and protruding through one side of the housing, a bearing rotatably supporting the nut member, a screw member coupled with the nut member to linearly move as the rotor rotates, and a mounting member supported on one side of the housing to support the screw member in such a manner that the screw member is linearly movable. The nut member includes an end portion passing through the bearing and a coupling portion extending from the end portion to couple with the bearing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/039,961, filed Sep. 27, 2013, which is a continuation of U.S.application Ser. No. 13/124,235, filed Apr. 18, 2011, now U.S. Pat. No.8,567,272, issued Oct. 29, 2013, which is the U.S. national stageapplication of International Patent Application No. PCT/KR2009/004344,filed Aug. 4, 2009, which claims priority to Korean Patent ApplicationNo. 10-2008-0100895, filed Oct. 14, 2008, all of which are incorporatedherein by reference in their entirety.

TECHNICAL FIELD

The embodiment relates to a step actuator.

BACKGROUND ART

A step actuator includes a rotor and a stator. The step actuatorlinearly drives a shaft according to rotation of the rotor.

For instance, the step actuator is connected to a member, which drives areflector of a vehicle headlight system, in order to change the lightingdirection. In addition, the step actuator converts the rotationalmovement of the rotor into the linear movement, so the step actuator canbe applied to various electric and mechanical devices requiring thelinear action.

DETAILED DISCLOSURE Technical Problem

The embodiment provides a step actuator having a novel structure.

The embodiment provides a step actuator including a rotor having a novelstructure.

The embodiment provides a step actuator in which a rotor is securelycoupled with a bearing.

Technical Solution

According to the embodiment, a step actuator includes a housing, astator in the housing, a rotor including a magnet provided radiallyinward of the stator and a nut member inserted into the magnet andprotruding through one side of the housing, a bearing rotatablysupporting the nut member, a screw member coupled with the nut member tolinearly move as the rotor rotates, and a mounting member supported onone side of the housing to support the screw member in such a mannerthat the screw member is linearly movable. The nut member includes anend portion passing through the bearing and a coupling portion extendingfrom the end portion to couple with the bearing.

According to the embodiment, a step actuator includes a housing, astator in the housing, a magnet provided radially inward of the stator,a nut member inserted into the magnet and protruding through one side ofthe housing, a bearing rotatably supporting the nut member, a couplingmember coupled with the nut member while interposing the bearingtherebetween, a screw member coupled with the nut member to linearlymove as the nut member rotates, and a mounting member supported on oneside of the housing to support the screw member in such a manner thatthe screw member is linearly movable.

According to the embodiment, a step actuator includes a housing, astator in the housing, a rotor including a magnet provided radiallyinward of the stator and a nut member inserted into the magnet andprotruding through one side of the housing, a bearing provided outsidethe housing to rotatably support the nut member, a bearing cover coupledwith the housing to support the bearing, a screw member coupled with thenut member to linearly move as the rotor rotates, and a mounting membercoupled with the bearing cover to support the screw member in such amanner that the screw member is linearly movable.

Advantageous Effects

The embodiment can provide a step actuator having a novel structure.

The embodiment can provide a step actuator including a rotor having anovel structure.

The embodiment can provide a step actuator in which a rotor is securelycoupled with a bearing.

DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing a step actuator according to theembodiment;

FIG. 2 is a sectional view showing the step actuator according to theembodiment;

FIGS. 3 and 4 are exploded perspective views showing the step actuatoraccording to the embodiment;

FIG. 5 is a perspective view showing the second housing that supportsthe bearing in the first direction in the step actuator according to theembodiment;

FIGS. 6 to 10 are views showing the coupling structure of a rotor and abearing in a step actuator according to a first embodiment;

FIGS. 11 to 14 are views showing the coupling structure of a rotor and abearing in a step actuator according to a second embodiment;

FIGS. 15 to 17 are views showing the coupling structure of a rotor and abearing in a step actuator according to a second embodiment;

FIGS. 18 to 20 are views showing the coupling structure of a rotor and abearing in a step actuator according to a fourth embodiment;

FIGS. 21 to 23 are views showing the coupling structure of a rotor and abearing in a step actuator according to a fifth embodiment;

FIG. 24 is a view showing the use of an elastic member in order tosecurely couple the rotor with the bearing in the step actuatoraccording to the embodiments; and

FIGS. 25 to 29 are views showing the structure and coupling relationshipbetween the bearing cover and the mounting member.

BEST MODE FOR INVENTION

Hereinafter, a step actuator according to the embodiment will bedescribed in detail with reference to accompanying drawings.

The thickness and size of each layer shown in the drawings may beexaggerated, omitted or schematically drawn for the purpose ofconvenience or clarity. In addition, the size of elements does notutterly reflect an actual size.

FIG. 1 is a perspective view showing a step actuator according to theembodiment, and FIG. 2 is a sectional view showing the step actuatoraccording to the embodiment. FIGS. 3 and 4 are exploded perspectiveviews showing the step actuator according to the embodiment.

Referring to FIGS. 1 to 4, the step actuator according to the embodimentincludes a stator, a rotor that rotates while interacting with thestator, a screw member 10 coupled to the rotor to linearly reciprocatein first and second directions according to forward and reverse rotationof the rotor, and a joint 70 coupled to the screw member 10.

The stator includes first and second bobbins 130 and 130, and first andsecond yokes 150 and 160 interposed between first and second housings110 and 120.

The rotor includes a magnet 30 installed inside the stator to rotatewhile interacting with the stator, and a nut member 20 coupled to themagnet 30.

The screw member 10 and the nut member 20 are coupled to each other inthe form of a bolt-nut assembly. Accordingly, if the nut member 20rotates, the screw member 10 linearly moves.

In detail, the first and second bobbins 130 and 130 are provided in aspace formed between the first and second housing 110 and 120, and thefirst and second yokes 150 and 160 are provided between the first andsecond bobbins 130 and 130.

In addition, the magnet 30, the nut member 20 and the screw member 10are provided radially inward in the first and second bobbins 130 and130.

In addition, a bearing 40, a bearing cover 50, and a mounting member 60are installed at one side of the second housing 120.

In more detail, as the step actuator according to the embodimentoperates, the screw member 10 linearly reciprocates in the first andsecond directions, which are opposite to each other, along an axis ofthe screw member 10.

In addition, a first end of the screw member 10 is inserted into aprotrusion pipe 132 of the first bobbin 130 and supported by theprotrusion pipe 132. A second end of the screw member 10 passes througha protrusion 61 of the mounting member 60 while supporting theprotrusion 61. A joint 70 is coupled to the second end of the screwmember 10.

A thread 11 is formed on an outer circumferential surface of the firstend of the screw member 10, and a stopper 12 is provided between thethread 11 and the second end of the screw member 10.

The thread 11 of the screw member 10 is coupled to a thread 21 formed onan inner circumferential surface of the nut member 20. Therefore, thescrew member 10 moves in the first or second direction as the nut member20 rotates.

The stopper 12 restrains the movement of the screw member 10 in thesecond direction. As the screw member 10 moves in the second direction,the stopper 12 is blocked by the protrusion 61 of the mounting member60, so that the screw member 10 cannot move in the second direction anymore. In addition, a blocking portion 133 is provided at a first end ofthe protrusion pipe 132 of the first bobbin 130 in order to restrain themovement of the screw member 10 in the first direction.

The movement of the screw member 10 in the second direction can berestrained by minimizing a diameter of a through hole 62 of theprotrusion 61 of the mounting member 60 such that the thread 11 of thescrew member 10 cannot pass through the protrusion 61 of the mountingmember 60. Similarly, the movement of the screw member 10 in the firstdirection can be restrained by minimizing a diameter of the first end ofthe protrusion pipe 132 such that the thread 11 of the screw member 10cannot pass through the protrusion pipe 132. Therefore, the blockingpart 133 and the stopper 12 can be selectively provided according todesigns.

Meanwhile, as described above, the screw member 10 can linearly move inthe first or second direction by passing through the mounting member 60,but the rotation of the screw member 10 about the axis is restrained.That is, the rotation of the screw member 10 is restrained by theprotrusion 61 of the mounting member 60.

For instance, the second end of the screw member 10 is cut into a shapeof “D” and the through hole 62 of the mounting member 60 has a shapecorresponding to a sectional shape of the second end of the screw member10.

Therefore, since the screw member 10 cannot rotate, the screw member 10linearly moves in the first or second direction as the nut member 20coupled to the screw member 10 rotates

As described above, the second end of the screw member 10 is coupledwith the joint 70. The joint 70 may be coupled with various appliancesto receive force transferred by the linear motion of the screw member10. In this case, the appliances may be variously selected according toapparatuses employing the step actuator according to the embodiment.

The screw member 10 is provided therein with a groove 13 at the side ofthe second direction, and a portion of the joint 70 is buried in thegroove 13. Accordingly, the screw member 10 can be securely coupled withthe joint 70 in the axial direction.

For example, the groove 13 may be formed by performing a knurlingprocess or a tapping process with respect to the screw member 10. Thejoint 70 is provided therein with a joint hole 71, and the screw member10 having the groove 13 is inserted into the joint hole 71. If heat oran ultrasonic wave is applied to the joint 70 in a state that the screwmember 10 is inserted into the joint hole 71, the joint 71 is melted,and the melted portion of the joint 71 is introduced into the groove 13.In this case, external force may be applied to the groove 13 such thatthe melted portion of the joint 70 is smoothly introduced into thegroove 13.

Then, if the heat or the ultrasonic wave is removed, the joint 70 ishardened, so that the screw member 10 can be securely coupled with thejoint 70.

The nut member 20 is inserted into the magnet 30 and a second end 22 ofthe nut member 20 protrudes in the second direction by passing throughthe magnet 30. A spline 23 is provided at an outer peripheral surface ofthe nut member 20 while extending in the axial direction and coupledwith a spline hole 31 formed in the magnet 30.

The nut member 20 partially overlaps with the magnet 30 in thecircumferential direction by the protrusion 23 and the spline hole 31,which are spline-coupled with each other. Accordingly, force applied inthe circumferential direction due to the rotation of the magnet 30 istransferred to the nut member 20, and the nut member 20 rotates as themagnet 30 rotates.

For example, the protrusion 23 and the spline hole 31 may have a curvedsurface. In this case, the spline hole 31 of the magnet 30 may be easilyprocessed.

The second end 22 of the nut member 20 is coupled with an inner race ofthe bearing 40. Thus, the nut member 20 can freely rotate while beingsupported by the bearing 40.

In addition, the thread 21 formed at the central portion of the innercircumferential surface of the nut member 20 is coupled with the thread11 of the screw member 10. In addition, the nut member 20 is coupledwith the protrusion pipe 132 of the first bobbin 130 at the innercircumferential surface provided at the side of the first direction androtatably supported by the protrusion pipe 132 of the first bobbin 130.That is, the inner circumferential surface of the nut member 20 providedin the first direction makes contact with an outer circumferentialsurface of the protrusion pipe 132.

The magnet 30 may include a permanent magnet having N and S poles whichare alternately aligned with each other in the circumferential directionat the regular interval. As described above, since the nut member 20 isinserted into the magnet 30, the nut member 20 rotates as the magnet 30rotates.

Meanwhile, a second end 32 of the magnet 30 protrudes in the seconddirection to make contact with the inner race of the bearing 40.Accordingly, the magnet 30 can smoothly rotate without making contactwith an outer race of the bearing 40 due to the second end 32 of themagnet 30.

The first bobbin 130 having a first coil 131 and the second bobbin 130having a second coil 141 are installed around the magnet 30. Inaddition, the first and second yokes 150 and 160 are interposed betweenthe first and second bobbins 130 and 130.

The first bobbin 130 includes a first coil winding portion 134, aroundwhich the first coil 131 is wound in a circumferential direction, and afirst terminal portion 135 electrically connected to the first coil 131.Similarly, the second bobbin 130 includes a second coil winding portion144, around which the second coil 141 is wound in the circumferentialdirection, and a second terminal portion 145 electrically connected tothe second coil 141.

As described above, the first bobbin 130 has the protrusion pipe 132,into which the screw member 10 is inserted, and a slit 136, into which athird tooth 111 of the first housing 110 is inserted. The first bobbin130 faces the magnet 30 and the nut member 20 in the first direction.The first bobbin 130 has a recess 134 recessed in the first direction toreduce friction among the first bobbin 130, the magnet 30 and the nutmember 20 as the magnet 30 and the nut member 20 move in the first orsecond direction.

The first yoke 150 includes a first body portion 151 having a ringshape, a first tooth 152 protruding from an inner peripheral surface ofthe first body portion 151 toward the first housing 110 to be interposedbetween the first bobbin 130 and the magnet 30, and a first groundingterminal 153 to ground the first body portion 151. In addition, thesecond yoke 160 includes a second body portion 161 having a ring shape,a second tooth 162 protruding from an inner peripheral surface of thesecond body portion 161 toward the second housing 120 to be interposedbetween the second bobbin 130 and the magnet 30, and a second groundingterminal 163 to ground the second body portion 161.

Meanwhile, the first housing 110 is provided with the third tooth 111protruding toward the second housing 120 to be interposed between thefirst bobbin 130 and the magnet 30 by passing through the slit 136 ofthe first bobbin 130. The third tooth 111 and the first tooth 152 arealternately aligned with each other along an outer peripheral portion ofthe magnet 30.

The first housing 110 has a first rim portion 112, which protrudesradially inward of the cylindrical body of the first housing 110, andthe third tooth 111 extends from the first rim portion 112 in the seconddirection. A first opening 113 is defined by the first rim portion 112and one side of the first bobbin 130 is inserted into the first opening113.

In addition, the second housing 120 has a fourth tooth 121 protrudingtoward the first housing 110 to be interposed between the second bobbin130 and the magnet 30. The fourth tooth 121 and the second tooth 162 arealternately aligned with each other along an outer peripheral portion ofthe magnet 30.

The second housing 120 has a second rim portion 122, which protrudesradially inward of the cylindrical body of the second housing 120, andthe fourth tooth 121 extends from the second rim portion 122 in thefirst direction.

Meanwhile, a first cutting portion 114 is formed in the first housing110 by cutting a predetermined portion of the first rim portion 112, anda second cutting portion 124 is formed in the second housing 120 bycutting a predetermined portion of the second rim portion 122. The firstand second rim sections 114 and 124 define an opening allowing the firstterminal portion 135 formed in the first bobbin 130, the first groundingterminal 153 formed in the first yoke 150, a second grounding terminal163 formed in the second yoke 160, and the second terminal portion 145formed in the second bobbin 130 to protrude outward through the opening.

The bearing 40 is installed at the second end of the second housing 120,and the bearing cover 50 is provided to support the bearing 40. That is,the bearing cover 50 is coupled to the second housing 120 to restrainthe bearing 40. For instance, the bearing cover 50 can be coupled withthe second housing 120 through a spot welding scheme or a laser weldingscheme.

As described above, the inner race of the bearing 40 is coupled with thesecond end 22 of the nut member 20 and supported by the second end 22 ofthe nut member 20.

In addition, the movement of the bearing 40 in the first direction isrestrained by the second rim portion 122 of the second housing 120, andthe movement of the bearing 40 in the second direction is restrained bythe bearing cover 50.

The diameter of a second opening 123 defined by the second rim portion122 is greater than that of the magnet 30 and smaller than that of thebearing 40. Accordingly, friction may not occur between the magnet 30and the second housing 120 and the movement of the bearing 40 in thefirst direction can be restrained.

FIG. 5 is a perspective view showing the second housing that supportsthe bearing in the first direction in the step actuator according to theembodiment.

Referring to FIG. 5, the nut member 20 is inserted into the magnet 30and is coupled with the inner race of the bearing 40.

The bearing cover 50 is coupled with the second housing 120 in thesecond direction, and the mounting member 60 is coupled with the bearingcover 50 in the second direction.

The bearing 40 is interposed between the bearing cover 50 and the secondhousing 120. The movement of the bearing 40 in the first direction isrestrained by the second rim portion 122 of the second housing 120.

Referring to FIG. 5, the bearing 40 is partially exposed between thesecond rim portion 122 and the magnet 30, and the remaining part of thebearing 40 is blocked by the second rim portion 122 of the secondhousing 120 so that the movement of the bearing 40 in the firstdirection can be restrained.

FIGS. 6 and 24 are views showing the coupling structure of a rotor and abearing in a step actuator according to other embodiments. Hereinafter,the embodiments shown in FIGS. 6 to 24 will be described while focusingon only the coupling structure of the rotor and the bearing, and thestructure and components identical to those of FIGS. 1 to 5 will be notfurther described in order to avoid redundancy.

In the following description, coupling sections and coupling members areused to securely couple the bearing 40, the magnet 30, and the nutmember 120 with each other. The coupling portion may be realized in theform of a coupling portion 22 a or a hook portion 22 c, and the couplingmember may be realized in the form of a snap ring 25, a nut memberstopper 26, and a bush 27.

FIGS. 6 to 10 are views showing the coupling structure of a rotor and abearing in a step actuator according to a first embodiment.

Referring to FIGS. 6, 7, and 8, the second end 22 of the nut member 10protrudes through the bearing 40 in the second direction. The outerperipheral portion of the second end 22 of the nut member 20 is coupledwith the inner race of the bearing 40 while making contact with theinner race of the bearing 40.

Referring to FIGS. 6, 9, and 10, after applying heat or an ultrasonicwave to a protrusion of the second end 22 of the nut member 20, theprotrusion is subject to the swaging process, thereby forming thebearing coupling portion 22 a coupled with the inner race of the bearing40 at the side of the second direction while making contact with theinner race of the bearing 40.

Therefore, the bearing 40, the magnet 30, and the nut member 20 can besecurely coupled with each other, and the bearing 40 can support themagnet 30 and the nut member 30 such that the magnet 30 and the nutmember 20 can smoothly rotate.

FIGS. 11 to 14 are views showing the coupling structure of a rotor and abearing in a step actuator according to a second embodiment.

Referring to FIGS. 11, 12, and 13, a coupling groove 22 b is formed inthe second end 22 of the nut member 20 in a circumferential direction ofthe second end 22. The snap ring 25 is provided at the side of thesecond direction of the bearing 40.

When the bearing 40, the magnet 30, and the nut member 20 are coupledwith each other, the second end 22 of the nut member 20 protrudesthrough the bearing 40 in the second direction, and the coupling groove22 b of the nut member 20 is exposed in the second direction.

Referring to FIGS. 11 and 14, the snap ring 25 is inserted into thecoupling groove 22 b, so that the bearing 40 is restrained at the sideof the second direction. The snap ring 25 is coupled with the couplinggroove 22 b, and makes contact with the inner race of the bearing 40 atthe side of the second direction.

Therefore, the bearing 40, the magnet 30, and the nut member 20 can besecurely coupled with each other by the coupling groove 22 b and thesnap ring 25, and the bearing 40 can support the magnet 30 and the nutmember 30 such that the magnet 30 and the nut member 20 can smoothlyrotate.

FIGS. 15 to 17 are views showing the coupling structure of a rotor and abearing in a step actuator according to a second embodiment.

Referring to FIGS. 15 to 17, a nut member stopper 26 is provided at asecond end of the bearing 40 and coupled with the nut member 22 at theside of the second direction.

The nut member stopper 26 makes contact with the inner race of thebearing 40 at the side of the second direction. A portion of the nutmember stopper 26 protrudes in the first direction and is inserted intothe nut member 22.

An outer circumferential surface of the nut member stopper 26 is coupledwith an inner circumferential surface of the nut member 22 while makingcontact with the inner circumferential surface of the nut member 22.Although not shown, the nut member stopper 26 may be provided at thecentral portion thereof with a through hole, so that the screw member 10can pass through the nut member stopper 26.

Therefore, the bearing 40, the magnet 30, and the nut member 20 can besecurely coupled with each other by the nut member stopper 26, and thebearing 40 can support the magnet 30 and the nut member 30 such that themagnet 30 and the nut member 20 can smoothly rotate.

FIGS. 18 to 20 are views showing the coupling structure of a rotor and abearing in a step actuator according to a fourth embodiment.

Referring to FIGS. 18 to 20, the hook portion 22 c is provided in thesecond end 22 of the nut member 20. The hook portion 22 c makes contactwith the second end of the bearing 40 through the bearing 40. In otherwords, the hook portion 22 c of the nut member 20 is coupled with theinner race of the bearing 40.

Therefore, the bearing 40, the magnet 30, and the nut member 20 can besecurely coupled with each other by the hook portion 22 c, and thebearing 40 can support the magnet 30 and the nut member 30 such that themagnet 30 and the nut member 20 can smoothly rotate.

FIGS. 21 to 23 are views showing the coupling structure of a rotor and abearing in a step actuator according to a fifth embodiment.

Referring to FIGS. 21 to 23, the coupling groove 22 b is formed in thesecond end 22 of the nut member 20 in a circumferential direction of thesecond end 22. The bush 27 having a ring shape is provided at the secondend of the bearing 40.

When the bearing 40, the magnet 30, and the nut member 20 are coupledwith each other, the second end 22 of the nut member 20 protrudesthrough the bearing 40 in the second direction, and the coupling groove22 b of the nut member 20 is exposed in the second direction.

The bush 27 is inserted into the coupling groove 22 b, and a caulkingprocess is performed with respect to the bush 27, so that the couplinggroove 22 b is securely coupled with the bush 27. In other words, thebush 27 is coupled with the coupling groove 22 b, and makes contact withthe inner race of the bearing 40 at the side of the second direction.

Therefore, the bearing 40, the magnet 30, and the nut member 20 can besecurely coupled with each other by the coupling groove 22 b and thebush 27, and the bearing 40 can support the magnet 30 and the nut member30 such that the magnet 30 and the nut member 20 can smoothly rotate.

FIG. 24 is a view showing the use of an elastic member in order tosecurely couple the rotor with the bearing in the step actuatoraccording to the embodiments.

FIG. 24 shows a case in which first, second, third, and fourth elasticmembers 28 a, 28 b, 28 c, and 28 d are used in the coupling structure ofthe rotor and the bearing according to the second embodiment shown inFIGS. 11 to 14. However, the first to fourth elastic members 28 a to 28d are applicable to other embodiments.

Referring to FIG. 24, the first elastic member 28 a may be interposedbetween the snap ring 25 and the bearing 40, the second elastic member28 b may be interposed between the bearing 40 and the magnet 30, and thethird and fourth elastic members 28 c and 28 d may be interposed betweenthe magnet 30 and the nut member 20.

All of the first to fourth elastic members 28 a, 28 b 28 c, and 28 d maybe applicable to the coupling structure of the rotor and the bearing, oronly one of the first to fourth elastic members 28 a, 28 b 28 c, and 28d may be applicable to the coupling structure of the rotor and thebearing according to applications. In other words, the locations and thenumber of the first to fourth elastic members 28 a, 28 b 28 c, and 28 dmay be selectively determined.

The first to fourth elastic members 28 a, 28 b, 28 c, and 28 d provideelastic force in an axial direction. Accordingly, the bearing 40, themagnet 30, and the nut member 20 can be securely coupled with each otherby the first to fourth elastic members 28 a, 28 b, 28 c, and 28 d, andthe bearing 40 can support the magnet 30 and the nut member 30 such thatthe magnet 30 and the nut member 20 can smoothly rotate.

FIGS. 25 to 29 are views showing the structure and coupling relationshipbetween the bearing cover and the mounting member.

Referring to FIG. 25, the bearing cover 50 includes a coupling rim 51, acoupling pipe 52, a locking rim 53, a support member 55, a stopperprotrusion 56, and a first contact member 57.

The coupling rim 51 has a ring shape with a predetermined width and iscoupled with the second rim portion 122 of the second housing 120. Forinstance, the coupling rim 51 is coupled with the second rim portion 122of the second housing 120 through a welding process.

The coupling pipe 52 extends in the second direction from an innerperipheral surface of the coupling rim 51 such that an innercircumferential surface of the coupling pipe 52 makes contact with anouter race of the bearing 40.

The locking rim 53 protrudes radially inward of a second end of thecoupling pipe 52 to make contact with the outer race of the bearing 40.The locking rim 53 restrains the movement of the bearing 40 in thesecond direction.

A plurality of support members 55 extend from an outer peripheralportion of the coupling rim 51 in the second direction while beingspaced apart from each other. In this case, a virtual line connectingthe support members 55 with each other may have a circular shape.

The stopper protrusion 56 extends radially outward from the supportmember 55. The stopper protrusion 56 includes first and second bendingmembers 56 a and 56 b which are arranged in the circumferentialdirection. The first and second bending members 56 a and 56 b aresupported on a locking member 64 and the locking protrusion 65 of themounting member 60 such that the mounting member 60 can be preventedfrom rotating in the circumferential direction when the mounting member60 is coupled with the bearing cover 50.

The first and second bending members 56 a and 56 b may enlarge thecontact area of the stopper protrusion 56, so that the stopperprotrusion 56 can be securely supported on the locking member 64 and thelocking protrusion 65.

The first contact member 57 extends radially outward from the second endof the support member 55 and makes contact with the second contactmember 67 of the mounting member 60 to prevent the mounting member 60from moving in the axial direction.

The mounting member 60 includes the protrusion 61, a receptacle pipe 63,the locking member 64, the locking protrusion 65, an extension rim 66,and the second contact member 67.

The protrusion 61 and the receptacle pipe 63 constitute a body of themounting member 60. The protrusion 61 supports the screw member 10 suchthat the screw member 10 can move in the first or second direction, andthe receptacle pipe 63 provides a space for installing the bearing 40and the bearing cover 50 therein. The protrusion 61 protrudes from thereceptacle pipe 63 in the second direction.

The first end of the receptacle pipe 63 is inserted between the supportmember 55 of the bearing cover 50 and the coupling pipe 52. Accordingly,an outer peripheral portion of the first end of the receptacle pipe 63makes contact with an inner peripheral portion of the support member 55and an inner peripheral portion of the first end of the receptacle pipe63 makes contact with an outer peripheral portion of the coupling pipe52.

The extension rim 66 extends radially outward from an outer peripheralsurface of the receptacle pipe 63 while forming a ring shape. Theextension rim 66 faces the first stopper protrusion 56 and the firstcontact member 57 of the bearing cover 50.

A plurality of locking members 64 extend from the outer peripheralportion of the extension rim 566 in the first direction while beingspaced apart from each other. An inner peripheral portion of the lockingmember 64 faces an outer peripheral portion of the coupling rim 51.

When the mounting member 60 rotates clockwise in a state that thelocking member 64 is positioned between the support members 55 of thebearing cover 50, the first bending member 56 a makes contact with thecircumferential end of the locking member 64. Accordingly, the mountingmember 60 does not rotate clockwise any more.

The locking protrusion 65 has elasticity and is formed on the extensionrim 66 between the locking members 64. The locking protrusion 65 has ashape of a cantilever having a free end making contact with the secondbending member 56 b of the stopper protrusion 56.

In other words, the locking protrusion 65 is positioned between adjacentsupport members 55, and then is locked with the second bending member 56b of the stopper protrusion 56 while moving along the stopper protrusion56 as the mounting member 60 rotates clockwise. Accordingly, themounting member 60 does not rotate counterclockwise any more.

The free end of the locking protrusion 65 is inclined such that thelocking protrusion 65 smoothly moves along the stopper protrusion 56.

The second contact member 67 extends radially inward of the first end ofthe locking member 64 while being spaced apart from the extension rim 66at a predetermined distance. The first contact member 57 is insertedbetween the second contact member 67 and the extension rim 66.

The mounting member 60 is positioned at the side of the second directionof the bearing cover 50. Thus, when the mounting member 60 is coupled tothe bearing cover 50, the second contact member 67, which is integrallyformed with the mounting member 60, is positioned at the first end ofthe first contact member 57, which is integrally formed with the bearingcover 50, so that the movement of the mounting member 60 can berestrained in the first and second directions.

In order to securely couple the bearing cover 50 with the mountingmember 60, an embossing 57 a is formed on the first contact member 57that makes contact with the second contact member 67. The embossing 57 aclosely adheres to the second contact member 67 when the locking member64 and the locking protrusion 67 are locked with the stopper protrusion56 due to the rotation of the mounting member 60, thereby supporting thesecond contact member 67 at the side of the first direction.

Hereinafter, the method for coupling the mounting member 60 with thebearing cover 50 will be described with reference to FIGS. 26 to 29.

As shown in FIG. 26, the receptacle pipe 63 of the mounting member 60 isinserted between the support member 55 and the coupling pipe 52 of thebearing cover 50, and the locking member 64 and the locking protrusion65 of the mounting member 60 are positioned between the stopperprotrusions 56 of the bearing cover 50.

Differently from FIG. 27, the first contact member 57 of the bearingcover 50 does not overlap with the second contact member 67 of themounting member 60 in the axial direction in FIG. 26.

Referring to FIGS. 26 and 27, if the mounting member 60 rotatesclockwise, as shown in FIG. 28, the locking member 64 makes contact withthe first bending member 56 a, and the locking protrusion 65 moves alongthe stopper protrusion 56 so that the free end of the locking protrusion65 makes contact with the second bending member 56 b. Accordingly, themounting member 60 is not rotated.

Similar to FIG. 29, the first contact member 57 of the bearing cover 50overlaps with the second contact member 67 of the mounting member 60 inthe axial direction in FIG. 28. Accordingly, the first contact member 57makes contact with the second contact member 67. However, since theembossing 57 a is formed on the first contact member 57, the embossing57 a closely adheres to the second contact member 67 to support thesecond contact member 67 while pushing the second contact member 67 inthe first direction. Therefore, the bearing cover 50 can be securelycoupled with the mounting member 60 without moving in the axialdirection.

The mounting member 60 can be easily disassembled by rotating themounting member 60 counterclockwise after lifting up the free end of thelocking protrusion 165 in the second direction.

The step actuator according to the embodiment includes the bearing cover50, which restrains the position of the bearing 40 and supports themounting member 60, and the mounting member 60, which guides andsupports the linear movement of the screw member 10. Thus, the mountingmember 60 can be manufactured in various shapes and easily coupled withthe bearing cover 50.

In the step actuator described above, an electric field is generated aspower is applied to the first terminal portion 135 and the secondterminal portion 145, so that the magnet 30 rotates in the forward orreverse direction according to the electric field.

As the magnet 30 rotates, the nut member 20 coupled with the magnet 30also rotates, so that the screw member 10 having the thread 11 engagedwith the thread of the nut member 20 moves in the first direction or thesecond direction according to the rotation direction of the magnet 30.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. Industrial Applicability

INDUSTRIAL APPLICABILITY

The embodiment is applicable to step actuators.

What is claimed is:
 1. A step actuator comprising: first and secondhousings; a stator including first and second bobbins and first andsecond yokes; a rotor including a magnet and a nut member; a bearingrotatably supporting the nut member; a screw member coupled with the nutmember to linearly move as the rotor rotates; a bearing cover coupledwith the second housing; and a mounting member disposed on the bearingcover to support the screw member in such a manner that the screw memberis linearly movable, wherein the magnet includes a spline hole providedat an inner peripheral surface thereof, and wherein the nut memberincludes a spline provided at an outer peripheral surface thereof andcoupled with the spline hole formed in the magnet.
 2. The step actuatorof claim 1, wherein a surface of the spline hole is curved, and whereina surface of the spline is curved.
 3. The step actuator of claim 1,wherein the first bobbin is facing the magnet and the nut member furtherincludes a recess.
 4. The step actuator of claim 3, wherein the recessis recessed in a first direction.
 5. The step actuator of claim 1,wherein the first bobbin includes a blocking portion to restrain themovement of the screw member in a first direction.
 6. The step actuatorof claim 1, wherein the nut member partially overlaps with the magnet ina circumferential direction where the spline and the spline hole arepresent.